Process for producing modified electronickel



Patented Nov. 16, 1948 PROCESS FOR PRODUCING MODIFIED ELECTRONICKEL Port Colborne, Ontario, The International Nickel Company, Inc., New York, N. Y., aeorporatlon Louis Secondo Renzoni Canada, assignor to of Delaware Application August 6, 1943, Serial No. 497,601

' In Canada June 12, 1943 4 Claims. (Cl. 204-37) The present invention relates to the production in situ of electro-deposited nickel containing sulfur and, more particularly, to the production in situ of electro-deposited nickel containing sulfur and suitable for use as anode in the electroplating of protective and/or decorative coatings of nickel elect'ro-plate.

Since nickel electro-plating was first employed for production of protective or decorative finishes,

tory to casting or casting and rolling anodes for use in electro-plating protective-and/or decora tive electroplates of nickel. Sulfur has also been incorporated in nickel for use as electro-plating anodes alone or in conjunction with oxygen. Such a nickel anode is disclosed in the Geiger U. S. Patents Nos. 1,941,256 and 1,941,257. Furthermore, Spencer points out in an article entitled The Corrosion of Nickel Anodes published in the Meta1 Industry (London) January 22, 1937, that magnesium or manganese should be present in anodes containing sulfur in order that the sulfur will combine to form a manganese or magnesium sulfide to the exclusion of nickel sulfides. In this article Spencer points out that nickel sulfide is insoluble in the plating solution and that when the major portion of the sulfur is combined with the nickel, the metallic nickel rains dissolve and leave the sulfide in veins on the surface or in detached particles which float across the bath and even lodge on the cathode to cause rough deposits.

In a recent U. S. patent granted to Bieber and Tschop, No. 2,304,059, for Nickel anodes, these patentees pointed out the necessity for providing a nickel anode having a critical coordinated relationship between the addition elements carbon, silicon, magnesium and sulfur. These patentees likewise point out that in the absence of suflicient magnesium to combine with substantially all of the sulfur, nickel anodes containing sulfur corrode in a non-uniform manner with the produc- 2 tion of excessive amounts of sludge and loose nickel.

From the foregoing it is manifest that the art has been provided with a large variety of fused nickel anodes for use in the electro-plating of protective and/or decorative electro-plates of nickeland that various hypotheses exist which form a basis for the addition of the various addition elements. However, the investigations of the last five years have clearl shown that while sulfur is an excellent agent for increasing the corrosion of nickel anodes and for enhancing the uniformity of corrosion and the activity of nickel anodes at high pH, such as pH 4 to 5.5 (Q), nevertheless the experts in the art are agreed that free sulfur is detrimental and that magnesium or manganese should be present in amounts willcient to bind substantially all of the sulfur as sulfide. It is to be noted that while Spencer suggests that manganese may be substituted for magnesium in order to overcome the detrimental effects of free sulfur, most electro-platers hold that in the presence of manganese unsatisfactory nickel electro-plates are obtained. As a consequence, most specifications relating to the composition of nickel anodes for the electro-plating of protective and/or decorative coatings, place a limit of about 0.001% as the upper limit for man- I ganese in a satisfactory nickel anode.

As has been pointed out in the Geiger U. S. Pat- 'ent No. 2,274,056, granted February 24, 1942, Extruded anode, there are a. minimum of 9 to 10 operations in producing a rolled anode. As a conseuence, the electro-plater has always felt that if a satisfactory nickel anode could be produced directly in the operation of electro-reilning nickel, desirable economies could be efiected which could be passed on to the electro-plater. Consequently, there has been a demand in the art for electrodeposited nickel in the unfused condition in a form to provide satisfactory activity at high pH, such as pH 4.0 to 5.5 (Q), smooth corrosion and the production of small amounts of sludge and loose nickel.

Attempts have been made to employ conventional electrolytic nickel as anode in electro-plating-nickel finishes. Many experts in the art in the last ten to fifteen years have attempted to use conventional electrolytic nickel as anode, but except when used in baths operating at relatively Edelmetalle in which he outlined some of the difilculties German electro-platers encountered in attempting to circumvent the conditions arisingfrom a lack of metallic nickel. The German electro-platers had used insoluble anodes such as carbon, lead and stainless steel and had found each of them unsatisfactory or as Raub states the situation: The use of insoluble anodes for the saving of nickel may also in view of all previous experiences be only an emergency measure the use of which is permissible only under most urgent compulsion."

This foreign authority on nickel anodes for electro-plating mentions a process developed by the Langbein Pfanhauser Werke Leipzig in which the relatively readily obtainable nickel salts are used as a source of nickel for the production. of nickel plated anodes which, in turn, may be used in the electro-plating of protective and/or decorative coatings of nickel. Raub condemns these anodes which are essentially conventional unfused electrolytic nickel as only slightly better than insoluble anodes. In addition to the condemnation by this foreign expert, Spencer likewise condemns the use of conventional prior art electro-hickel as an anode in the production of protective and decorative electro-plates. In the article to which reference has been made hereinbefqre, Spencer makes the following statemenis:

The pure nickel used in industry in the United States is supplied in the form of electropossible. From a commercial point of view it is questionable whether the cost of depositing such an anode and annealing it would be low enough to make it economically practicable.

From the. foregoing itis apparent that this expert in the art discounts entirely the possibility that cathode nickel could be used as an anode in the electro-deposition of decorative and/or protective coatings of nickel. Furthermore, it will be noted that this expert inthe art bases his opinion that electro-nickel will not provide a satisfactory anode upon characteristics of electro-nickel, i. e., internal stresses, which a are in no way related to the chemical composition of the anode.

Tests of Spencer's suggestion have proven that prior art cathode nickel substantially devoid of sulfur, i. e., containing less than 0.005% sulfur, when annealed in accordance with Spencer's suggestion as disclosed in the prior art, shows little or no improvement in corrosion properties as anodes irinickel electroplating baths over unannealed electro-nickel of the same composition. Furthermore, an annealing and quenching treatment most recently disclosed in the Hull U. 8. Patent No. 2,297,766 is not entirely satisfactory. That is to say, the annealing and quenching treatment disclosed in the aforesaid Hull patent raises the limit of activity of electro-nickel from pH 2.5 (Q.) for normally sulfur-free electronickel to pH 3.5 (Q.) for electro-nickel treated in accordance with the Hull disclosure. At DH values higher than 3.5 (Q.) electro-nickel treated in accordance with the Hull process produces larger amounts ofloose nickel than untreated electro-nickel when used as anode in nickel electroplating baths.

deposited plates or sheets about'one-fourth inch in thickness and cut up in squares of suitable size. It has the typical structure of such deposits" in that it consists of groupings of parallel elongated crystals, their size and shape apparently being dependent on the uniformity or non-uniformity of the electric current,'composition of the solution, temperature, and other such factors.

.Any change in these will alter the rate of deposition and the crystal size. If the current is stopped, metal deposition will cease, and re-solution of nickel from the cathode may occur, or

nickel anodes.

copper or other metal impurities in the solution may deposit by immersion with the formation of a film of oxides or basic salts on the surface. When deposition is resumed, a new layer of crystals of different orientation will be formed, probably with weak adherence to the underlying metal. This is one reason why cathode sheet nickel would be unsatisfactory for use as anodes.

Cathode sheet nickel, provided it could be electro-deposited in long, narrow sheets of sufficient thickness and without separate layers of metal, should be suitable for use as anodes in awell-balanced' plating solution. Because of the internal stresses developed in deposition, it should be more easily attacked brsolution than annealed or heat-treated metal. On the other hand, since the stresses probably are not uniform) throughout the piece, the corrosion would be uneven, and an undesirable amount of anode scrap Thus it is manifest that the electro-plating art had found cast and rolled anodes of fused nickelsatisfactory from a technical aspect in many instances, but sought a cheaper sourceof in the slightly acid range of pH 3 to pH 5.5 (Q) even when annealed. In addition, experts in the art have condemned electro-nickel as anode for reasons entirely disconnected from the chemical composition of electro-nickel. However, it has been discovered that satisfactory electro-nickel or cathode nickel anodes can be produced in situ during the electro-refining of impune nickel.

It is an object of the present invention to provide a process for producing electro-nickel or cathode nickel in situ which is satisfactory for use as anode in the electro-plating of protective and/or decorative electro-plates of nickel.

It is'another object of the present invention to provide cathode nickel containing a critical amount of sulfur produced in situ without fusion for use as anode in the electro-plating of protective and/or decorative electro-plates of nickel in baths having a pH more alkaline than pH It is also readily recognized that "the art had not found prior art conventional unfused electro-nickel suitable for use as anodetective and/or decorative electro-plating's of nickel from baths having a pH more alkaline than pH 2 (Q). I

The present invention also contemplates the production of heat-treated electro-nickel or cathode-nickel containing sulfur.

It is also within the contemplation of the present invention to provide cathode nickel or electro-nickel containing copper and sulfur.

The present invention also provides for the production of electro-nickel or cathode-nickel containing carbon, copper and sulfur.

Other objects and advantages will become apparent from the following description'taken in conjunction with the drawings in which:

Figure 1 is a more or less diagrammatic flow sheet illustrative of the application of the principles of the present invention to the production of modified cathode nickel or electro-nickel; and

Figure 2 is illustrative in a more or less diagrammatic manner of another embodiment of the application of the principles of the present invention to the production of modified cathode nickel or electro-nlckel.

Broadly speaking, the novel modified electronickel or cathode nickel can be produced by introducing suitable re-agents into the electrolyte of a nickel electro-refining operation. That is to say, whether the electrolyte employed for the electrorefining of nickel be the conventional all-sulfate electrolyte which has been the one most generally employed for this purpose or the all-chloride electrolytewhich has not been used to so great an extent, or the novel sulfate-chloride electrolyte disclosed in the co-pending U. S. application Serial No. 472,471, now Patent No. 2,394,874, granted Febi'uary 12, 1946, the novel modified cathode nickel or electro-nickel can be produced in substantially the same manner by addition of the same re-agents, whether the electrolyte be of the all-sulfate, -the all-chloride, or the sulfate-chloride type.

Sulfur can be introduced into electro-nickel or cathode nickel without fusion of the nickel by introducing a sulfur-bearing compound soluble in the electrolyte and reducible to HzS at the cathode into the purified electrolyte. Illustrative of such addition agents are $02 introduced either as a gas or as an aqueous solution thereof, sulfites and acid sulfites of the alkali metals. As those skilled in the art know, a primary consideration in determining what agents may be employed for introducing any material into electronickel is the effect of the material upon the purification of the electrolyte. For example, the sodium to nickel ratio in a nickel electro-refining electrolyte must be maintained in a critical proportion in order to avoid producing. a brittle electro-nickel. It has been found that a nickel to sodium ratio of about'1 to 1 provides an electro-nickel having suitable ductility. When the ratio becomes smaller, the electro-nickel becomes quite brittle and when the ratio becomes larger,'-the electro-nickel becomes more ductile. Consequently in selecting a material to be added to a nickel electrolyte for electro-reflning nickel,

the operator is confronted with the problem of,

maintaining this nickel to sodium ratio. In addition to the foregoing, it is necessary that the carrier of the sulfur be of such character that it is either eliminated during the electro-deposition of the sulfur, is readily eliminated before the attempt is made to purify the electrolyte, or does not interfere with the purification of the impure electrolyte. A more comprehensive appreciation of this problem is most readily obtained by a consideration of the conventional process for the production of conventional prior art electro-nickel substantially devoid of sulfur.

The most. generally practiced method for electro-refining nickel involves the use of an allsulfate electrolyte. The process as usually carried out involves the use of a cell having a diaphragm separating the anode compartment from the cathode compartment. An impure anode is employed and the anolyte removed continuously for purification which involves removal of iron, arsenic, lead and copper. I do not knowof any practical method for the continuous removal of cobalt from all-sulfate nickel electrolytes. Various schemes have been recommended, but all of them are extremely diificult to operate and none of them is being used commercially. Removal of the impurities set forth hereinbefore provides a purified electrolyte which is introduced into the cathode compartments of the various cells at such a rate as to maintain a hydrostatic head sufllcient to overcome the tendency of the cations, copper, iron, etc., to migrate from the impure anolyte into the relatively highly purified catholyte. In the cathode compartments, a relatively pure nickel is electro-deposited from the purified electrolyte.

The foregoing process as generally employed is 9 described in more detail in the article by R. L. Peek entitled "Refining nickel-copper'matte at Port Colborne in the November 10, 1930, issue of Engineering and Mining Journal, published by McGraw-Hill Book Company, Inc.

Briefly stated, the electro-refining of nickel involves the production of impure nickel anodes which are cast in any suitable manner and generally have a nickel content of about to aboutv 96%. Dependent upon the source of the nickel from which thevimpure nickel anodes are produced, such anodes will contain greater or lesser amounts of the impurities present in the ore.

Thus, for example, in one industrial operation, the impure nickel anodes contain about 94% to about 96% of nickel, about 2.5% to about 3.5% of copper, about 0.7% to about 0.9% of cobalt, about 0.5% to about 1.0% of iron, about 0.002% to about 0.004% of lead, about 0.05% to about 0.07% of arsenic and about 0.5% to about 0.8% of sulfur.

:The electro-refining of nickel involves solution of the metallic constituents of the impure anode in the anolyte followed by purification of the anolyte to remove iron, copper, cobalt, lead, arsenic, etc. to obtain a purified electrolyte from which electro-nickel can be produced.

Electrolytic nickel produced in the all-sulfate electrolyte has the following composition:

Composition Per Cent About 99.18 to about 99.29 About 0.80 to about 0.70 About 0.005 to about 0.003 About 0008 to about 0 005 About 0.004 to about 0.002 About 0.003 to about 0.002 About 0.000 to about 0.0001 About 0.000 to about 0.000

The general features of the electrolytic cell preferably employed in. conjunction with the Hybinette bag are described more or less in detail, together with the process employed in conjunction therewith, in the Hybinette U. S. Patent No. 805,969. In the prior art all-sulfate process, the electro-refining of nickel is generally and preferably carried out employing Hybinette bags. As

those skilled in the art know, the Hybinette bag generally comprises a wooden frame of spruce or the like covered with a canvas of such weight that a slight hydrostatic pressure maintained on the cathode side of the canvas substantially prevents the migration of copper, cobalt, nickel, iron and similar cations from the impure electrolyte through the canvas diaphragm into the purified electrolyte present as a catholyte in the cathode compartment of the cell.

As clearly set forth in U. S. Patent-No. 805,969, a hydrostatic pressure is maintained in the cathode compartment and impure anolyte withdrawn from the anode compartment continuously. The impure anolyte is first subjected to purification to remove copper and, in the all-sulfate ion electroylte, the copper is removed by cementation'through addition of nickel, preferably in the form of freshly reduced nickel powder, before the iron, lead and arsenic are removed. After the copper has been removed by cementation, the iron, lead and arsenic are then removed. When desired, the cobalt is removed in the all-sulfate ion electrolyte by the addition of nickel, preferably in the form-of an oxide or hydrated oxide prepared outside the electrolyte system by the action of a strong oxidizing agent upon nickelous hydrate, whereby the nickel goes into solution and the cobalt is precipitated.

The refining of nickel-containing material by electro-deposition of nickel from a .purified electrolyte involves the use of a number of electrolytic cells employing a diaphragm to separate impure anolyte from the catholyte. The number of cells required is, of course, dependent upon the amount of nickel to be electro-deposited in a unit of time, most of the cells being operated with a soluble anode while a few of the cellsare operated employing insoluble anodes. The soluble anodes are obtained, by casting or otherwise forming, from impure metallic material containing a rela tively high percentage of nickel and also containing so much of the impurities, copper, iron, cobalt,

. lead, arsenic and sufur that the impure anodes are not acceptable, per se, to the trade as pure nickel. The impure anodes are immersed in the anode compartment of the diaphragm cell in contact with lean anolyte obtained from previous of cupric copper ions by oxidizing the iron with oxygen at a pH which permits the iron to hydrolyze to the hydroxide. Without separating the iron precipitate, arsenic and lead are oxidized with chlorine and then precipitated together with the iron. By suitable control of the .pH of the solution, cobalt can likewise be. precipitated with the iron, arsenic and lead. Thereafter, the con per is removed in any conventional manner, preferably by cementation using freshly reduced nickel as the agent. In the event that all of the cobalt has not been removed by re-precipitation with iron, arsenic and lead, the residual cobalt is precipitated by the addition of chlorine and nickel carbonate to provide an electrolyte substantially free from iron, lead, arsenic, copper and cobalt.

The purification of the all-chloride electrolyte is carried on in a manner similar to that employed in purifying the all-sulfate electrolyte.

It is preferred in producing the novel modified cathode nickel or electro-nickel to maintain an electrolyte temperature of about 125 F. to about 140 F. and a pH of about 3.5 to about 5.0 (Q.). The lower pH limit of operation is determined by the pH at which sulfide sulfur may be deposited from purified nickel electrolytes containing a sulfur-bearing addition agent such as sulfur dioxide, sodium sulfite, or sodium acid sulfite, or in general an electrolyte soluble sulfur bearing compound capable of reduction to H'zS -at the cathode. This value is determined by the solubility product of nickel sulfide under the conditions existing at the cathode. Lower pH values may be employed by adding ions capable of forming sulfides having a lower solubility than nickel sulfide to the electrolyte. Sulfur-bearing cathode nickel or electronickel has been produced from an all-sulfate nickel electrolyte containing 42 grams per liter operations, i. e., catholyte, the nickel content of which has been suitably lowered by electro-deposition of nickel. Under the influence of the electric current and the anions present in the lean anolyte, the soluble impure anodes are more or less completely dissolved in the lean anolyte with the production of an impure anolyte containing practically all of the nickel and the "base metals, copper, cobalt, iron, lead and arsenic. The precious metals, gold, platinum and other metals of the platinum metal group togetherwith sulfides of copper and nickel, present in the soluble impure anodes, remain on the more or less completely dissolved impure anodes as anode slimes in quanti ties dependent upon previous operations and the source of the nickel.

The process for electro-refining nickel'employing a sulfate-chloride electrolyte is somewhat similar to that utilized in electro-refining nickel with an all-sulfate electrolyte. However, there are some differences. Thus, for example, it has been found more satisfactory to remove lead, iron and arsenic from the electrolyte before removing copper. In the sulfate-chloride electrolyte employed in the process disclosed in the co-pending U. S. application Serial No. 472,471, the iron in the impure anolyte is precipitated in the presence of nickel, 40 grams per liter of sodium sulfate and 20 grams per liter of boric acid at pH 4.8 and a temperature of F. from anodes containing the impurities copper and iron. Preferably, the sulfur-bearing addition agent is added to the purified electrolyte before introduction into the cathode compartment in such a manneras to ensure uniform distribution of the sulfur-bearing material throughout the electrolyte flowing to the cathode cell. Thus, for example, the sulfur-bearing material may be introduced into the electrolyte immediately after the last purification step or the purified electrolyte may be introduced into a holding tank and the sulfur-bearing compound l kewise added to the electrolyte in the holding tank. 0n the other hand, the holding tank may be eliminated and the sulfur-bearing compound introduced into the stream of purified electrolyte a suitable distance before the .purified electrolyte enters the cathode compartments.

While the sulfites and acid sulfites .of the alkali metals or even the alkaline earth metals may be employed, it is preferred to use gaseous sulfur dioxide or an aqueous solution of sulfur dioxide.

Sulfur dioxide is the preferred addition agent beamount of S02 present in the electrolyte expressed as grams per liter.

PGriilfiS er er Per Cent Sulfur in Cathode g a pH Electra-Nickel Catholyte 0.00 6. 0 About 0.000 to about 0.000 0. 04 4. 6 About 0. 005 to about 0. 04 0.075 4. 2 About 0. 070 to about 0.08 0. l 3. 8 About 0. 10 to about 0. 0. l8 3. 5 About 0. 15 to about 0. 0. 21 3. 2 About 0. 20 to about 0. 22 0. 34 2. 9 About 0. to about 0. 35

Electro-nickel or cathode-nickel produced as above described by introducing a sulfur-bearing compound such'as sulfurdioxide or the sulfites or acid sulfites of the alkali metals or alkaline earth metals under an otherwise normal operating condition of temperature and current density is satisfactory for use directly without fusion as anodes when the sulfur-content of the electro-nickel or cathode-nickel is about 0.03 to about 0.5%. When the electro-nickel is corroded in a standard hot Watts bath, the ,electro-mckel is active throughout the range of pH about 1.5 to pH about 5.5 (Q). In addition, the electro-nickelcorrodes uniformly and what is of greater importance does not produce an amount of sludge or loose nickel appreciably in excess of that which experience has proven is the maximum amount which can be tolerated in industrial electro-plating of protective and/or decorative films of nickel.

Electra-nickel containing 0.005% to 0.03% sulfur may also be rendered satisfactory for use without fusion after undergoing heat treatment at temperatures of about 1500 F. to about 1800 F. for periods of time of about 20 minutes to about 30 minutes in a non-oxidizing, i. e., neutral or reducing atmosphere. After such heat treatment Thus, it is apparent desired size and thus eliminating the necessity of shearing. It has been discovered that this tendency to brittleness or the tolerance for sulfur of electro-nickel can be overcome. When copper is added to electro-nickel and correlated to the amount of sulfur present therein electronickel containing sulfur in excess of 0.03% sulfur can be produced which not only has all the desirable anode corrosion characteristics, but in addition has a satisfactory ductility in the unann'ealed condition. In the presence of about 0.01% to about 0.10% copper, the sulfur content of cathode nickel can be raised to as much as 0.12% to provide electro-nickel which is satisfactory for use as anode in the unannealed and unfused condition throughout the pH range of the electro-nickel has substantially the same corrosion properties as electro-nickel containing 0.03 to 0.5% of sulfur, e. g., the annealed electronickel corrodes actively at pH 5.5 in distinct contrast to prior 'art sulfur-free electro-nickel annealed in accordance with prior art process such as that taught by Spencer and Hull to which reference has been made hereinbefore.

electro-nickel could be made satisfactory for use as anode by some undisclosed annealing treatment, it is to be noted that even when prior art conventional electro-nickel substantially devoid of sulfur is heat-treated as described hereinbefore in conjunction with the novel electro-nickel of the present invention, the so heat-treated prior art electro-nickel substantially devoid of sulfur, i. e., containing no sulfur or "less than about 0.005% sulfur, nevertheless does not have satisfactory anode corrosion characteristics and even after such heat-treatment prior art conventional electro-nickel substantially devoid of'sulfur is not satisfactoryv for use as anode because it is not active throughout the range of pH about 1.5 to pH about 5.5 (Q.

Electro-nickel containing sulfur in excess of 0.03% is somewhat brittle and presents some difliculty in shearing although it is satisfactory for use directly without fusiom This difficulty may be overcome by growing the cathodes to the Although Spencer has suggested that conventional prior art I per liter of copper and about 0.1 to

. employed to about 1.5 to about pH 5.5 (Q.) and in addition the electro-nickel has practically no tendency to brittleness and may be readily sheared into sizes suitable for use as anode.

The copper-bearing modified electro-nickel containing sulfur may be produced in a manner quite analogous to that described hereinbefore for the production of modified electro-nickel containing sulfur. That is to say, an electrolyte soluble copper salt, such as copper sulfate or copper-chloride or a copper compound, which when introduced into the electrolyte is converted to a soluble form, is added to the electrolyte in carefully controlled amounts sufficient to provide an amount of copper within the range of about 0.001'to about 0.03 gram per liter of electrolyte. The copper compound may -be introduced simultaneously with the sulfur-bearing compound or may even be introduced as a copper sulfite. In other words, a solution of copper sulfate, for example, may be introduced into the electrolyte after the final purification thereof wherein the electrolyte has been freed from such impurities as iron, lead, arsenic, copper and cobalt, or the copper salt or the copper compound may be introduced into a holding tank together with sulfur dioxide as indicated hereinbefore. Furthermore, although somewhat more difficult to control, the removal of copper from the impure electrolyte may be regulated to leave in the purified electrolyte a residual amount of copper within the critical limits set forth hereinbefore. In other respects the production of copper-bearing modified electro-nickel containing sulfur is carried out under the same conditions as those taining sulfur, but substantially no copper.

It has been found that the tolerance of electro-nickel for sulfur can be increased by introducing into the electro-nickel a. controlled amount of carbon in addition to acon'trolled amount of copper. That is to say, electro-nickel containing about 0.02% carbon, 0.15% copper, and about 0.12% sulfur can be produced in an allsulfate electrolyte or an all-chloride electrolyte or a mixed sulfate-chloride electrolyte by in troducing into the electrolyte acetylene as well as a copper salt and a source of sulfur capable of being reduced to H28 at the cathode- The acetylene is introduced intb the electrolyte in amounts sufiicient to provide a concentration of about 0.001 to about 0.003 gramof acetylene per liter of electrolyte. Simultaneously, provision is made to provide about 0.03 to about 0.05 gram about 0.15 gram of $0; per liter of electrolyte. The temperature, current density and pH of the electrolyte during electro-deposition of the carboncopper-bearing modified electro-nickel containproduce modified electro-nickel con-' 11 are substantially the same as the values ing sulfur variables during the electro-deposition for thes of conventional prior art electro-nlckel substanduced into the holding tank and sulfur dioxide in-gaseous form or as an aqueous solution thereof likewise introduced into the holding tank. The purified electrolyte containing about 0.005 to about 0.5 gram per liter of S: is then introduced into the cathode compartment or chamber of the electro-reflning cells wherein the nickel in" the purified electrolyte together with the-sulfur of the sulfur dioxide contained therein is deposited at the cathode ,to provide. the novel modified electro-nickel orcathode-nickel described herein. As has been pointed out hereinbefore, sulfur-bearing compounds capable of reduction to H28 at the cathode,' such as sulfites. acid sulfites of the alkali metals and alkaline earth metals may be employed with equally satisfactory results in the place of sulfur dioxide provided the concentration oi the sulfite or acid sulfite is controlled to provide a concentration of so: in the purified electrolyte or catholyte equivalent to that set forth hereinbefore. In the production of novel copper-bearing modified electrolytic nickel containing sulfur, the copper salt or other copper compound which is introduced into the purified electrolyte or catholyte may like- I wise be added to the electrolyte in the holding tank.- Similarly, the purified electrolyte or catholyte may be treated with acetylene in the holding tank when it is desired to provide a modified carbon-bearing electro-nickel. Accordingly. it will be understood that when it is desired to produce novel carbon-copper bearing.

modified electro-nickel or cathode-nickel, the

materials which are the source of carbon, copper and sulfur may all be added to the purified electrolyte or catholyte in the holding tank, or when desirable one or more of the addition agents may be added prior to or subsequent to passage of the purified electrolyte through the holding tank,

and the remaining addition agent added-to the I purified electrolyte or catholyte in the holding tank.

. Fig. 2 is illustrative of another method of'introducing addition agent into the purified electrolyte or catholyte. As is manifest in the embodlment of the present invention illustrated by the drawing (Fig. 2) no holding tank is employed and the addition agents are introduced directly into the stream of purified electrolyte or catholyte.

- While the drawing illustrates only one point at which the addition agentsmay beintroduced, the addition agents, may be introduced at several points provided sufficient time elapses between the time of addition of the last addition agent and introduction into the cathode chamber of the electro-depositin'g cells to permit thorough mixing of the last addition agent introduced throughout the purified electrolyte or catholyte.

As those skilled in the art know,-prior art conventional electro-nickel is produced in an all-sillfate electrolyte having a composition within the following limits:

Composition Grams Per Liter bout 40 to about 00 bout so to about no bout it to about 30 bout 30 to about 40 l0 lemperature of about 130 F. to about 140 13.

Composition Grams Per Liter About 40 to about 60 About 60 to about 76 About to about Temperature of about 130 F. to about 140 F. 16E of about 4.5 to about 5.2 pH (Q.).

urrent density of about 15 to about 1) amperes per square loot.

Prior art conventional electrol-nickel substantially devoid of sulfur can be produced in a sulfate-chloride bath having the following composition:

- I Com osition -Grams Per Liter cent to about 00 bout 71 to about 12) bout 2'! to about 30 bout iii to about 26 About 10 to about 36 About to about Sodium chloride --I As disclosed in the co-pending U. S. application Serial No. 472,471, conventional prior art electro-nickelsubstantially devoid of sulfur can be produced in the foregoing electrolyte employing:

Temperature of about F. to about F.

pH of about 4.0 to about 5.0 pH

Current density of about 15 to a ut 20 amperes per square foot. Prior art electro-nickel varies but slightly in composition whether produced in an all-sulfate electrolyte, an all-chloride electrolyte, or a mixed sulfate-chloride electrolyte. Thus prior art conventional electro-nickel produced in an all-sulfate bath generally has a composition as indicated hereinafter:

Composition Per Cent Prior art conventional electro-nickel produced in an all-chloride bath generally has a composition within the ranges indicated hereinafter:

0.000 to about t 0.000 to About 0 003 to about bout '0101 to about About 99.8 to about 99.

Electro+nickel substantially devoid of sulfur and produced in a sulfate-chloride electrolyte, such as described in the co-pending U. S. application Serial No. 472,471 has a composition fall- The novel modified electro-nickel containing sulfur has a composition falling within the range indicated hereinafter:

Composition Per Cent Sulfur About 0.005 to about 0.5 Iron About 0.001 to about 0.005 Manganese About 0.000 to about 0.0015 Magnesium About 0.000 to about 000 arbon About 0.000 to about 0 000 C0 per. About 0.003 to about 0 005 Go alt.. About 0.01 to about 0 80 Nickel About 90.81 to about 98.59

Copper-bearing modified electro-nickel con- .taining sulfur has a composition falling within the following range:

Composition Per Cent Sulfur About 0.10 to about 0.15 Iron About 0.001 to about 0.005 Manganese. About 0.000 to about 0.0015 Ma esium About 0.000 to about 0.000' Car on.. About 0.000 to about 0.000 Copper. About 0.05 to about 0.15 Cobalt... About 0.01 to about 0.80 Nickel About 99.84 to about 98.80

Carbon-copper bearing modified electro-nickel containing sulfur has a composition falling within the range indicated hereinafter:

Composition devoid of said impurities, positively introducing an effective amount of an electrolyte-soluble sulfur-bearing compound selected from the group consisting of sulfur dioxide and sulfites and acid sulfltes of the alkali metals and alkaline earth metals into said purified electrolyte, electro-depositing nickel from said purified electrolyte to obtain electro-nickel containing about 0.005% sulfurto about 0.03% sulfur, and subjecting said electro-nickel to heat treatment at temperatures of about 1500 F. to about 1800 F. in a non-oxidizing atmosphere.

2. A process for producing electrol-nickel having good activity as anode up to pH 5.5 (Q.)- in nickel electro-plating baths and corroding as anode at pH up to 5.5 (Q) without the production of undesirable amounts of loose nickel and sludge, which comprises purifying an electrolyte containing nickel and at least one of the group of impurities consisting of copper, iron, arsenic and lead to obtain a purified electrolyte substantially devoid of said impurities, positively introducing an effective amount of an electrolytesoluble sulfur-bearing compound selected from the group consisting of sulfur dioxide and sulfites and acid sulfites of the alkali metals and alkaline earth metals into said purified electrolyte, electro-depositing nickel from said purified electrolyte to obtain electro-nickel containing about 0.005% sulfur to about 0.03% sulfur. and subjecting said electro-nickel to heat treatment at temperatures of about 1500 F. to about 1800 F. in a non-oxidizing atmosphere for about 20 minutes to about 30 minutes.

3. A process for producing electro-nickel hav-' ing good activity as an anode in nickel electroplating baths and corroding smoothly up to about When the symbol (Q.) is used herein in con-' nection with pH values, it denotes that the pH value is determined with the well .known and.

1. A process for producing electro-nickel hav-v ing good activity as anode up to pH 5.5 (Q) in nickel electro-plating baths and oorroding as anode at pH up to 5.5 (Q.) without the production of undesirable amounts of loose nickel and sludge,

which comprises purifying an electrolyte containing nickel and at least one of the group of impurities consisting of copper, iron, arsenic and lead to obtain a purified electrolyte substantially pH 5.5 without the production of undesirable amounts of loose nickel and sludge which comprises anodically corroding impure'nickel to obtain an electrolyte contaminated with copper and iron, removing said copper and iron by cementation and hydrolysis, respectively, to secure a purified electrolyte, mixing about 0.005 to about 0.03 gram per liter of sulfur dioxide as a saturated aqueous solution thereof with said purified electrolyte, electrodepositing a a nickel cathode con-,

taining about 0.005 to about 0.03% sulfur from the thus-treated solution, and annealing said nickel cathode for a period of about 20 minutes to about 30 minutes at a temperature of about 1500 F. to about 1000 F. in a reducing atmosphere, the annealed nickel cathode being suitable for subsequent use as an anode.

4. A process for producing electro-nickel having good activity as an anode in nickel electroplating baths and corroding smoothly up to about pH 5.5 without the production of undesirable amounts 'of loose nickel and sludge which comprises corroding impure nickel as anode to obtain an electrolyte contaminated with copper and iron, removing said copper and iron by cementation and hydrolysis, respectively, to secure a purified electrolyte, mixin an amount of an electrolyte-soluble sulfur-bearing compound selected from the group consisting of sulfur dioxide and sulfltes and acid sulfites of the alkali metals and alkaline earth metals to provide a concentration equivalent to about 0.005 to 0.03 gram per liter of sulfur dioxide with said purified electrolyte,- electrodepositing a nickel cathode containing about 0.005 to 0.03 sulfur from the thus-treated solution, and annealing said nickel cathode for a period of about 20 minutes to about 30 minutes at a temperature of about 1500" F. to about 1800 15 16 I". in a reducing atmosphere. the annealed nickel Number Name Date cathode being suitable for subsequent use as an 2,112,818 Waite Mar. 29, 1938 a d 2,115,019 Gronningsaeter Apr. 26, 1938 LOUIS SECONDO RENZONI. 2,304,059 Bieber Dec. 8, 1942 2,385,269 Globus Sept. 18, 1945 REFERENCES CITED 2,392,708 Tschop Jan. 8, 1946 The following references are of record in the OTHER, REFERENCES me of this patent" Modern Electroplating, Special Volume, The UNITED STATES PATENTS 1 Electrochemical Society, published 1942, pages Number Name Date 242,

90,332. Adams May 25,1869 Metal In try, Jan. 22. 1937; pages 141-144. 1,750,092 Crawford Mar. 11, 1930 Circular of Bureau of Standards No. 100

1,941,257 Geiger Dec. 26, 1933 (192 pages 6 and 9.

2,001,385 Gronnlngsaeter May 14, 1935 15 Certificate of Correction Patent No. 2,453,757. November 16, 1948.

LOUIS SECONDO RENZONI It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 7, line 17, for electroylte read electrolyte; line 44, for sufur read sulfur; column 9, line 22, for the Word sulfurdioxide read sulfur dioxide; column 12, line 33, in the table, first column thereof, for Glread C'l column 14, line 13, claim 2, for electrol-nickel read eZectro-niclcel; line 47, claim 3, before nicke strike out a; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 29th day of March, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommissioner of Patents. 

